1. Field of the Invention
The present invention relates to an earphone amplifier system for a telephone and particularly to an earphone amplifier which is turned on automatically when the handset is taken off-hook.
2. Description of the Prior Art
For the hard of hearing, the normal volume level in a telephone receiver may not be loud enough to be heard comfortably or at all. This problem of insufficient telephone volume is particularly acute for elderly or infirm persons who may depend on the telephone to summon aid in an emergency, and to overcome loneliness by communicating with relatives and friends. Auxiliary amplification of the incoming audio can solve this problem, and thereby make use of the telephone more accessible to, or more comfortable for such persons.
Telephone earphone amplifiers are known per se. They function to amplify the incoming audio signal to a level sufficient to be heard comfortably by the hard of hearing, or to amplify a particularly weak signal to a level that is comfortable for a person with normal hearing. To make such an amplifier widely available, it is important that its cost be low, and that its installation be simple and inexpensive. A principal object of the present invention is to provide such an amplification system.
Battery powered amplifiers may be low in cost, but have the requirement that the power must be switched on and off each time the telephone is used. A simple manually operated switch may be provided for this purpose. However, this requires that the switch be turned on each time the telephone is used, and turned off at the end of each conversation. If the user forgets to turn off the switch, the amplifier will remain on, draining down the battery, perhaps to the point where no power is left to operate the amplifier when the telephone next must be used. With such an arrangement, there may be no warning given to the user that the power switch has been left on at the end of the conversation. If such a warning signal were provided, the signalling mechanism itself may place an unnecessary drain on the battery thereby shortening its usable lifetime.
An alternative is to utilize a mechanical switch that is operated when the handset is removed from the cradle. Such a mechanism would ensure turn-off of the amplifier when the handset is replaced at the end of a call. However, such a mechanism is cumbersome, and may be unsightly and/or expensive.
A further object of the present invention is to provide an earphone amplifier system in which power to the amplifier automatically is turned on only for the duration of each call. No mechanical switch is employed, thereby eliminating the need for the user manually to turn off the amplifier, and eliminating the need for a mechanism to actuate the switch when the handset is taken from its cradle.
Another desirable feature for a telephone earphone amplifier is that its installation be simple and inexpensive. An object of the present invention is to facilitate such simple installation. In telephone instruments in which the handset is connected by a jack and plug arrangement, one embodiment of the present invention permits installation merely by removing the handset plug from the telephone instrument, plugging it instead into an adapter unit containing the invention, and plugging that unit into the telephone instrument. Alternatively, the present invention may be installed merely by connecting four wires in circuit with the telephone handset.